I was beaten to the punch. 11 is the correct answer. 120-109=11.
A bigger shovel will allow you to dig a larger hole than by using a smaller shovel, if scoops per minute are the same for both sizes. Also, a larger shovel will dig a faster hole of equal size to the smaller shovel, again dependant on equal speed of scooping. Now Physicsman might be able to shed more light on this though using one of his calculations that a smaller shovel might be able to did a faster or larger hole because having a lgihter load, might make the scoops per minute faster than a larger heavier shovel.